1. Field of the Invention
The invention relates to a silo for sludge, especially sewage sludge, comprising a sludge-receiving part, a feeding part in communicating with said sludge-receiving part via an inlet, and a sludge-discharge device.
2. Description of the Related Art
Sludges which are temporarily stored in silos of this type are generally transported from the silo via a pipeline system to a disposal location, for example to a incineration facility. In order to prevent the entrainment of foreign bodies along with the sludge in the pipeline, which can lead to blockages in undefined areas thereof, it is known to provide incorporated sieves at various locations in the pipeline system, which respectively retain foreign bodies depending on the sieve size. In order to prevent a clogging of the sieves, these must be removed and cleaned at relatively short time intervals.
Beginning therewith, it is the task of the invention to provide precautionary measures in a silo for sludges and sewage sludges, which make it possible to dispense with the labor-intensive sieve devices in the down-stream equipment and systems.
The inventive solution is based upon the concept, that if a separating device for foreign bodies were to be located in the feeding part of the silo, the sludge withdrawn through the sludge discharge device would be in better condition for a problem-free further transport through the pipeline system. Since in sludges, such as sewage sludges which have a solids content of up to 70%, the foreign bodies are embedded in the sludge and cannot be separated from the sludge purely using sieves, it is proposed in accordance with a preferred embodiment of the invention, that the foreign body separating device has a sieve-grate covering the inlet and at least one counter-surface position above the sieve-grate, which sieve-grate and counter-surface are moveable in relation to each other as sludge pushes through the sieve openings of the sieve-grate. The foreign bodies, partially still soiled with sewage sludge, are retained by the sieve-grate and can either be removed by hand or mechanically before the next charge of sludge is introduced into the feeding part. For this it is useful when the foreign body separating device includes at least one foreign body outlet provided on the side of the sieve-grate opposite to the sludge-receiving part.
In accordance with a further preferred embodiment of the invention, the foreign body separation device includes a feed frame supplied with sludge and bordered by raised sidewalls, which is so positioned or positionable between the sieve-grate and the counter-surface, that the sieve-grate and/or the counter surface are moveable relative to each other transverse to the frame opening. A first variation of this embodiment envisions that the counter-surface is formed by the inner surface of a silo lid covering over the feed part, and that the sieve-grate is moveable by means of a preferably hydraulic drive through the feed frame which is provided fixed to the silo and in the direction of the silo lid. In order to make it possible to remove the sludge contaminated foreign bodies from the sieve-grate, a slideable sweeper or rake can be provided, in this case slideable parallel to the upper surface of the sieve-grate and in the direction of the foreign body outlet, which sweeper or rake can be driven by motor or hydraulically, when the sieve-grate is situated displaced towards its end position against the counter-surface.
In accordance with a related embodiment, a sieve-grate is provided fixed to the silo and covering over the inlet opening, while the counter-surface is provided in the form of a push- or pressure-plate, which is displaceable from above through the feed frame in the direction of the sieve-grate, preferably by means of a hydraulic drive. In this alternative embodiment there is preferably provided a feed frame which is displaceable relative to the supply part and the sieve-grate, which is open towards above and below, and which can be filled with sludge at a filling station situated on a base aligned with the sieve-grate and from which fill position it is moveable in the direction of the sieve-grate. For the transport away of the foreign bodies contaminated within the sewer sludge, the feed frame, with raised pressure plate, can be displaced relative to the sieve-grate in the direction of the foreign body outlet. The foreign body outlet preferably exhibits in this case an outlet opening which on its edges contacts the sieve-grate, via which the floor-side open supply frame is moveable with carrying along of the foreign bodies.
The hydraulic drive of the sieve-grate or, as the case may be, pressure plate occurs preferably using four simultaneously operable hydraulic cylinders engaging along the edge or corner area of the sieve-grate or, as the case may be, the pressure plate. Depending upon application, it is also possible to employ more or fewer hydraulic cylinders as the drive aggregate.
A further advantageous embodiment of the invention envisions that the counter-surface is formed by a wiper or skimmer surface perpendicular or diagonal to the direction of the sieve-grate and spring biased against the sieve-grate, wherein the sieve-grate and the skimmer or wiper are moveable relative to each other parallel to the upper surface of the sieve-grate. Preferably herein the sieve-grate is rotateable about a central axis relative to or with respect to the at least one silo-fixed wiper or skimmer. To order to facilitate the transport of larger foreign bodies to the foreign body outlet, there is provided supplementally, according to an advantageous embodiment of the invention, an abutment wall or stop for this type of foreign body at least in the close proximity above the sieve grate, radially oriented, which at the same time can function as the assembly or mounting wall for the wiper. Preferably, two wiper groups are provided separated from each other through the rotation center point of the sieve-grate, which serve therefore, that the sludge situated on the rotating sieve-grate is wiped or stripped spring-biased in the right direction and thereby pressed through the sieve-grate. The rotating sieve-grate is preferably surrounded by a jacket fixed to the silo, which includes at least one opening serving as foreign body outlet, which for control of a charge-wise foreign body output is preferably formed closeable or lockable.
The foreign body outlet can in all above-described variations open into a foreign body chamber, which can be acted upon with water for removal of the sewage sludge from the foreign bodies and can be connected via a sewage sludge conveyor section with the sludge receiving part of the silo.